1. Field of the Invention
The present invention relates to an electromagnetic wave amplifier for amplifying an electromagnetic wave in one direction and an electromagnetic wave generator for generating an electromagnetic wave which are applicable in a lot of fields of electronic engineering, communication engineering, electromagnetic wave, engineering, electron device engineering, quantum electronic engineering, optical electronics, and laser engineering, etc.
2. Related Art Statement
Electronics progresses toward the object of developing technology which transmits and processes more mass information at higher speeds. To this end, in electronic technology, the technology which treats a higher frequency domain has been developed, and it has come to treat even the region of light which reaches a high frequency of 1015 Hz as electronic engineering.
However, in the range from the microwave to the optical regions, transistors and ICs, which are the leading part of electronics, can not be used. As a result, special elements and methods are used instead, and various technical restrictions exist.
In the optical region (1014-1015 Hz), the laser is used as an active device for generating and amplifying the signal, but in the laser, both the travelling signal and the retreating signal are amplified. In a word, in the laser, signal amplification does not become unidirectional (non-reversible), but becomes bilateral (reversible). The bilateral amplifying characteristic of the laser is contrasted with the unidirectional amplifying characteristic of the transistor and the electric vacuum tube, considering that the logical operation on the computer becomes possible by utilizing the unidirectional amplifying characteristic, the information processing controlling light itself cannot be achieved with the use of the laser as an active device in the optical region (1014-1015 Hz).
In the microwave region (109-1011 Hz), the traveling wave tube is used as a unidirectional active device. The traveling wave tube is a unidirectional electric vacuum tube having the highest operation frequency more than the upper limit (about 1 GHz=109 Hz) of an operation frequency of a usual electric vacuum tube which is an unidirectional and a functional electronic device and a transistor. The travelling wave tube decreases a propagation velocity of the electromagnetic wave by using a delay transmission line made of metal. Energy will be given to the electromagnetic wave by the electron beam emitted from the electron gun, and energy loss according to the collision of the electron with a surrounding material and scattering is reduced by making the environment a vacuum condition.
The electromagnetic wave is amplified in the traveling wave tube when the speed of the electron beam and the velocity of propagation of the electromagnetic wave coincide, so that the electromagnetic wave propagating in the opposite direction is not amplified. However, the travelling wave tube cannot operate in frequency regions over 1011 Hz at the present time, because the upper limit of the operating frequency is determined by precise technology for metal manufacturing.
The frequency band of 1011-1014 Hz belongs to a region of infrared rays from a submillimeter wave, but this region is an undeveloped region with respect to electronics. In another word, neither any amplifier nor any generator (oscillator) operating with coherent (the phase is controlled) electromagnetic wave has yet been put to practical use in this frequency region. The reason for a difficult use of the above region is that this region has a frequency band with irregular phenomena such as an electron scatterings (collisions) in the material and thermal molecular motions, etc. However, technological development in the frequency region of 1011-1014 Hz provides not only a technology for the solution of environmental problems of the detection of the contamination quality in the atmosphere, but also a technology which enables the transmission of extra-large capacity in an optical communication system which uses it as a carrier frequency.
There are free electron lasers and Cerenkov masers (microwave amplification by stimulated emission of light radiation) having the property of unidirectional amplification operation as devices in which generation and the amplification of an electromagnetic wave are possible from the microwave region to the optical region. The free electron laser is an optical generator capable of being oscillated in wide-ranging wave lengths, and the light receives an energy of the electron beam propagated in one direction in a vacuum by using a mechanism of operation different from other types of lasers, so that the free electron laser has a characteristic of amplifying only the light component propagated in the same direction as that of the electron beam. However, the free electron laser was developed aimed at the generation of light, so that the design of the amplifier having the above unidirectional amplifying property is not performed. In addition, in the free electron laser and the Cerenkov maser, operating voltage (excitation voltage of the electron beam) is extremely high, being 1 MV or more, and an extremely strong magnetic field is needed to give the electron beam the vibration, so that the utilization for electronics is difficult since the above laser and maser are developed aiming at a special high-energy usage.
To solve above described various problems, the present inventor has previously proposed a unidirectional optical amplifier which uses an electron beam in a solid material in Japanese Patent Application Laid-open No. 270808/1998. In this unidirectional optical amplifier, it is theoretically shown to achieve unidirectional amplification of light (electromagnetic wave), by combining the electron beam travelling path for the electron beam emitted in the solid material and the dielectric substance delay waveguide for delaying light to be amplified.
Moreover, to solve the above described various problems, the present inventor has previously proposed an electric vacuum tube type unidirectional optical amplifier which uses an electron beam emitted in a vacuum in Japanese Patent Application No. 293819/1997. In this electric vacuum tube type unidirectional optical amplifier, by using a pair of mirrors having wave shaped form arranged in a vacuum and for forming a delay waveguide of light, and by utilizing the energy received from the electron beam emitted from the electron emitting section, it is theoretically shown to achieve unidirectional amplification of light (electromagnetic wave) by constituting an optical amplifying section which amplifies input light in one direction.
In addition, to solving the above described various problems, the present inventor has previously proposed a unidirectional optical amplifier which uses an electron beam emitted in a vacuum in Japanese Patent Application No. 231251/1998. In this unidirectional optical amplifier, it is theoretically shown to achieve unidirectional amplification of light (electromagnetic wave), by combining the electron beam travelling path for the electron beam emitted in the vacuum and a dielectric waveguide for delaying light to be amplified.
In the unidirectional optical amplifier of the prior application (Japanese Patent Application Laid-open No. 270808/1998) of the present inventor, an electron cannot travel when the acceleration voltage exceeds 2.5V in the case of constituting the electron beam travelling path with, for example, ZnSe, so that the acceleration voltage of the electron beam cannot be increased, and the spatial phase change in the electromagnetic field becomes extremely imperceptible, and thus the manufacture of the delay waveguide would need an accuracy on the order of ten nm. In the electric vacuum tube type unidirectional optical amplifier of the above prior application (Japanese Patent Application No. 293819/1997) of the present inventor, a mirror having a wave shaped surface would need to be manufactured with an accuracy on the order of ten mn. Although, the manufacturing technology with accuracy on the order of ten nm is available nowadays, easier fabrication of the device with a lower operating voltage is expected with further progress of a manufacturing technology in the future. In the unidirectional optical amplifier of the above prior application (Japanese Patent Application No. 231251/1998) of the present inventor, an operating voltage on the order of tens of KV is required since light is delayed by a straight dielectric waveguide. Thus, the decrease of operating voltage becomes a problem.
It is an object of the present invention to solve the above problems by realizing as an electromagnetic wave amplifier, which achieves unidirectional amplification of the electromagnetic wave in the region from the microwave to the optical frequencies, and which has seemed to be impossible up to now, with the use of the electron in a vacuum and the electromagnetic wave seeping in vacuum from a dielectric waveguide.
It is another object of the present invention to provide, as an electromagnetic wave generator, a device which uses electrons in a vacuum and an electromagnetic wave seeping from a dielectric waveguide in the vacuum, and which generates an electromagnetic wave in the region from the microwave to optical frequencies, which has seemed to be impossible up to now.
According to the present invention, there is provided an electromagnetic wave amplifier arranged in a vacuum environment, and comprising an electron emitting section for emitting electron beams, and an amplifying section for amplifying an inputted electromagnetic wave in one direction by utilizing energy received from electron beam emitted from the electron emitting section and travelling in the vacuum, characterized in that the amplifying section consists of a dielectric substrate having a dielectric waveguide formed thereon in an electron beam travelling direction and a pair of electrodes for the electron beam focusing arranged to clip the dielectric waveguide from opposite sides; the dielectric waveguide causes an electric field component of the electromagnetic wave in the electron beam travelling direction by overlapping a part of the inputted electromagnetic wave and the electron beam emitted from the electron emitting section; and the surface of the dielectric waveguide is processed to a wave shaped form of a given periodic length so as to decrease the travelling speed of the electromagnetic wave in the electron beam travelling direction.
According to the amplifier of the present invention, the dielectric substrate has an input waveguide and an output waveguide which are connected to the ends of the dielectric waveguide respectively through curved portions in the orthogonal direction.
In an embodiment of the electromagnetic wave amplifier according to the present invention, the dielectric waveguide is a material of high refractive index having transparency in an operating wave length region. The dielectric waveguide may consist of II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or III-V group compound semiconductors such as GaN when using the dielectric waveguide for the visible light region, and it may consist of IV group semiconductors such as Si and Ge, II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or III-V group compound semiconductors such as GaAs, InP, GaN, and these mixed crystals when using the dielectric waveguide from the microwave region to the near infrared light region.
According to the present invention, there is provided an electromagnetic wave generator arranged in a vacuum environment, and comprising an electron emitting section for emitting electron beams, and an oscillating section for generating an electromagnetic wave by utilizing electron beams emitted from the electron emitting section and travelling in vacuum, characterized in that the oscillation section consists of a pair of electrodes for the electron beam focusing arranged to clip the dielectric waveguide from opposite sides and a dielectric substrate on which a dielectric waveguide is formed in the electron beam travelling direction; the dielectric waveguide generates an electric field component of the electromagnetic wave in the electron beam travelling direction by overlapping a part of the electromagnetic wave generated from the electron emitting section and travelling in the vacuum, and the electron beams emitted from the electron emitting section; the surface of the dielectric waveguide is processed to a composite wave shape formed by combining two kinds of cycle lengths in order both to decrease the travelling speed of the electromagnetic wave in the electron beam travelling direction by one cycle length and to give a resonance effect for oscillating the electromagnetic wave by the other cycle length.
In a preferable embodiment of the electromagnetic wave generator according to the present invention, the dielectric substrate comprises a power output waveguide connected to the terminal portion of the dielectric waveguide through a curve part from an orthogonal direction thereof.
In a further preferable embodiment of the electromagnetic wave generator according to the present invention, the dielectric waveguide is a material of high refractive index having transparency in an operating wave length region, and it may consist of II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or II-V group compound semiconductors such as GaN when using the dielectric waveguide for the visible light region, and it may consist of IV group semiconductors such as Si and Ge, II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or III-V group compound semiconductors such as GaAs, InP, GaN, and these mixed crystals when using the dielectric waveguide from the microwave region to the near infrared light region.
According to the amplifier of the present invention, the electromagnetic wave input to the amplifying section arranged in a vacuum seeps in part from the dielectric waveguide in the vacuum when the electromagnetic wave propagates in the dielectric waveguide formed in the electron beam travelling direction of the dielectric substrate which constitutes the amplifying section, and the electric field component of the electromagnetic wave is caused by intersecting the seeped electromagnetic wave and the electron beam travelling in the vacuum and emitted from the electron emitting section. In that case, the travelling speed of the electron beam travelling direction of the electromagnetic wave decreases depending on a wave shaped form of a given cycle length on the surface of the dielectric waveguide and on the effective refractive index of the dielectric waveguide, so that the electric field component of the electromagnetic wave receives energy from the electron beam (the electron beam travels in the vacuum, so energy loss according to scattering due to the collision with a surrounding material is reduced) and the electromagnetic wave is amplified in one direction.
Further, according to the amplifier of the present invention, the travelling speed of the electromagnetic wave in the electron travelling direction is delayed in the dielectric waveguide formed in the amplifying section, and the electric field component of the electromagnetic wave is generated by intersecting the electromagnetic wave which seeps in the vacuum and the electron beam travelling in the vacuum, so that the electromagnetic wave amplifier performing the unidirectional amplification of the electromagnetic wave, can be achieved by using the electron in the vacuum and the electric field component of the electromagnetic wave. Moreover, the electromagnetic wave amplifier chiefly depends on a wave shaped form of a given cycle length on the surface of the dielectric waveguide and decreases the travelling speed of the electron beam travelling direction of the electromagnetic wave, so that operating voltage can be greatly decreased compared with the unidirectional optical amplifier of Japanese Patent Application No. 231251/1998.
According to the amplifier of the present invention, the dielectric substrate has the input waveguide and the output waveguide connected from the orthogonal direction to both ends of the dielectric waveguide, respectively, through curve parts, so that after the electromagnetic wave is amplified by the dielectric waveguide, the electromagnetic wave led from the input waveguide can be output from the output waveguide.
The dielectric waveguide of the present amplifier is a material of high refractive index having transparency in an operating wave length region, and it may consist of II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or III-V group compound semiconductors such as GaN when using the dielectric waveguide for the visible light region, and it may consist of IV group semiconductors such as Si and Ge, II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or III-V group compound semiconductors such as GaAs, InP, GaN, and these mixed crystals when using the dielectric waveguide from the microwave region to the near infrared region.
According to the generator of the present invention, in accordance with the electron beam emitted from the electron emitting section and travelling in the vacuum, the electromagnetic wave is generated in the electron beam travelling direction in the dielectric waveguide formed on the dielectric substrate constituting the oscillating section. A part of the electromagnetic wave seeps from the dielectric waveguide in the vacuum, and the electric field component of the electromagnetic wave is caused by intersecting the seeped electromagnetic wave and the electron beam travelling in the vacuum and emitted from the electron emitting section. In that case, the travelling speed of the electron beam travelling direction of the electromagnetic wave decreases, depending on one of two kinds of cycle lengths of surfaces of the dielectric waveguide and the effective refractive index of the dielectric waveguide, so that the electric field component of the electromagnetic wave receives energy from the electron beam (the electron beam travels in the vacuum, and thus, energy loss according to scattering due to the collision with a surrounding material is reduced). Here, when the other of the two kinds of cycle lengths satisfies a condition concerning the wave length of the electromagnetic wave and the gain coefficient becomes larger than the loss coefficient of the dielectric waveguide, the electromagnetic wave gets a resonance effect by the reflection in the dielectric waveguide, and the oscillation caused is in the desired frequency domain (range from the microwave region to an optical region).
According to the generator of the present invention, the electric field component of the electromagnetic wave is generated by overlapping the electromagnetic wave seeped in a vacuum and the electron beam travelling in the vacuum, and the electromagnetic wave is oscillated by delaying the travelling speed of the electromagnetic wave in the electron travelling direction in the dielectric waveguide formed to the oscillating section, so that the electromagnetic wave generator for generating the electromagnetic wave of the desired frequency domain, can be achieved.
Further, according to the generator of the present invention, the dielectric substrate comprises a power output waveguide connected to the terminal portion of the dielectric waveguide through a curve part from an orthogonal direction thereof, so that the electromagnetic wave becoming an electromagnetic wave in the desired frequency domain and generated in the dielectric waveguide can be output from the output waveguide.
According to the magnetic wave generator of the present invention, the dielectric waveguide is a material of high refractive index having the transparency in an operating wave length region. It may consist of II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or III-V group compound semiconductors such as GaN when using the dielectric waveguide for the visible light region, and it may consist of IV group semiconductors such as Si, Ge, and II-VI group compound semiconductors such as ZnSe, CdS, and these mixed crystals or III-V group compound semiconductors such as GaAs, InP, GaN, and these mixed crystals when using the dielectric waveguide from the microwave region to the near infrared light region.